Support means for slope revetments

ABSTRACT

A method and means is provided for protecting slope revetments of banks and of harbor basins and waterways against crumbling under the water line. The method includes the step of supporting the foot of the revetment with an oblong body which extends in the longitudinal direction of the slope and which is suspended from a carrier. This carrier rests at least in part on the slope and is covered by the revetment.

United States Patent [19] Rinkel [451 Mar. 27, 1973 [s41 SUPPORT MEANS FOR SLOPE REVETMENTS [75] Inventor: Gerardus Rinkel, s-Hertogenbosch,

Netherlands [73] Assignee: Bitumarin NV, Zaltbommel, Netherlands 22 Filed: Mar. 9, 1971 21 App1.No.: 122,551

[30] Foreign Application Priority Data May 11, 1970 Netherlands ..7006762 52 vs. C] ..61/38 51 Int. Cl. ..E02b 3/12 [58] Field of Search ..6l/37, 38, 1, 3,4, 5, 6

[56] References Cited UNITED STATES PATENTS 2,454,292 11/1948 Pickett ..6l/38 3,538,711 11/1970 Nielsen ..61/38 3,517,514 6/1970 Vissen, 61/38 2,047,197 7/1936 Fordyce 61/38 2,159,685 5/1939 Bunell .61/37 3,344,609 10/1967 Greiser .61/38 3,561,219 2/1971 Nishizawa et a1 ..61/38 Primary ExaminerReinaldo P. Machado Assistant Examiner-Philip C. Kannan AttorneyJones and Lockwood 57 ABSTRACT A method and means is provided for protecting slope revetrnents of banks and of harbor basins and water,- ways against crumbling under the water line. The method includes the step of supporting the foot of the revetment with an oblong body which extends in the longitudinal direction of the slope and ,which is suspended from a carrier. This carrier rests at least in part on the slope and is covered by the revetment.

12 Claims, 1 Draxving Figure SUPPORT MEANS FOR SLOPE REVETMENTS The invention relates to a method and a means for the protection of slope revetments of banks of harbor basins and waterways against crumbling under the water line.

As is known, the slopes of banks of harbor basins and waterways are protected by a revetment against the action of Waves and currents. This revetment, for example bulk material such as stone, possibly grouted with bitumen or formed as a coherent Water-impermeable or water-permeable lining, for example mastic or sand asphalt, rests on the slope. A revetment of this type is not normally applied to the slope over the full width thereof, in other words it does not reach the bottom of I the water-course. It often happens that as a result of erosion, for example caused by the down-drag of waves, or by the wash of the propellers of maneuvering vessels, part of the slope underneath the bottom edge of the revetment is cut away so that the revetment at this place is no longer carried by the slope but will hang at that place by the part of the revetment situated higher up. Since even a coherent revetment has a very low tensile strength, the revetment crumbles at these places. This crumbling tends to aggravate erosion of the slope so that repairs become necessary.

Means have now been found to avoid this crumbling by supporting the foot of the revetment.

The invention therefore relates to a method and a means for the protection of slope revetments of banks of harbor basins and waterways against crumbling under the water line, in which the foot of the revetment is supported by means of an oblong body extending in the longitudinal direction of the slope, which body is suspended from carrier means which rest at least in part on the slope and are covered and/or enveloped by the revetment.

The drawing shows a side view of the revetment supported by the carrier means on the slope of an embankment.

The following is meant by carrier means 6 which rest at' least in part on the slope 2 of a bank 3 of a harbor basin and are covered and/or enveloped by the revetment 1. The carrier means 6, for example cables, rods, wires or a net are secured to the oblong body and, starting from this body, extend upwards along the slope 2. If the revetment 1 consists of a heavy mass such as rip rap, for example random or pitched stone, this mass will force the carrier means 6 onto the slope 2 so that the carrier means 6 are covered by the revetment. If plastic or visco-elastic revetments 1 are used, the carrier means 6 do not rest on the slope over their full length since they are drawn, at least in part, into the revetment 1 by the weight of the oblong bodies 4 suspended therefrom and are then enveloped by the revetment l.

The carrier means 6 themselves are anchored either by the frictional resistance exerted by the carrier means on the slope or by being connected to, for example stakes 12 provided at the top of the slope, or by a combination of both.

The oblong element 4 is preferably at least substantially cylindrical, the average diameter being preferably 0.8 to 1.5 times the thickness of the revetment. The object of the invention is likewise achieved with a diameter in excess of L times the thickness of the revetment, but such a large diameter is not economic. The choice of a diameter smaller than 0.8 times the thickness of the revetment 1 still enables crumbling to be checked in the case of coherent revetments which are relatively rigid at the water temperature but such a diameter may be insufficient in this respect for revetments showing relatively little coherence.

It will be clear that in waterways, of which the slopes are lined over substantially the full length of the waterway, it is not feasible to use oblong bodies in one length. In this case oblong bodies are employed of such length that they can be handled by the available equipment and be arranged in end-to-end or overlapping relationship, whereupon they may be fastened to each other, if desired.

The oblong body 4 may be a relatively rigid body, for example a pile. Although such a body provides good support for the revetment 1, it has the drawback that it cannot follow a change in profile of the slope brought about by incipient scour, as a result of which progressive scour is not suppressed. In fact, the oblong body 4 preferably also performs a secondary function, i.e. it should follow as closely as possible any change in profile of the slope so that accelerated erosion as a result of gaps formed in the slope by the scour is prevented. Such a function can only be performed if the oblong body 4 is sufiiciently flexible to follow an incipient scour. Such a function is highly effective if it is accompanied by a corresponding flexibility of a coherent revetment, thus permitting the assembly of revetment and oblong body to conform to the changing profile of the slope. In the case of rigid or inflexible revetments, which are hardly, if at all capable of following an incipient scour a flexible oblong body is less effective.

A suitable flexible body is built up, for example, of a skin 13 which envelops a deformable mass 14. This skin may consist of a film or a fabric. The skin material 13 is preferably a rot-proof material, for example a plastic. If the skin 13 is a fabric, this may also be made of glass fiber. Preferably, the skin 13 is a fabric made of a polyalkylene thread or filament, in particular a thread or filament of high-pressure polyethylene or of polypropylene, which fabric has a weight of to g/m in particular 1 10 g/m. As filling mass for the skin shaped as a hollow cylinder use may of course be made of any deformable filling mass 14, for example sand. Particularly suitable is a filling mass which contains sand and a cutback bitumen and preferably also an additive which promotes the envelopment of the sand grains by the bitumen, for example lime. A mixture of this type remains satisfactorily kneadable at the temperature of the water 10. A very suitable mixture contains 90-96 percent by weight of sand, l-3 percent by weight of lime and l-9 percent by weight of cutback bitumen. A suitable cutback bitumen is commercially available under the name Special Road Oil (for example S.R.O. B). This Special Road Oil conforms to the requirements of the Specifications laid down by Rijkswaterstaat (State Water Authority) 1967. The said sand mixtures may be prepared from moist or wet sand.

As carrier means 6 for the oblong body use is preferably made of a net, although non-coherent carrier means such as cables, may also be employed. A net is preferred because of its coherence and in view of the.

fact that it provides relatively more points of application for frictional forces than non-coherent carrier means. A net also offers advantages in positioning the oblong body 4, which for obvious reasons is most conveniently effected before laying the lining. In this case the net together with the oblong body 4 attached thereto is merely laid on the slope and lowered over the required distance along the slope 2, whereupon the net is secured to the body of the bank 2, for example with stakes 12.

A suitable net is one having a 10-25 cm mesh. The nets are preferably made of rope consisting of a rotproof material such as synthetic fibers, in particular rope made from polypropylene monofilament. The rope thickness may be selected to suit the force that will be exerted on it. An invariably strong and durable net is obtained from polypropylene rope of 4-6 mm thickness and has a mesh of l-25 cm.

As set out hereinbefore, it is preferred to use an oblong body 4 which is sufficiently flexible to follow changes in profile of the slope 2, and thus supports a revetment which has a corresponding flexibility. Such a lining is, for example, a layer consisting of a mixture of sand, lime and cutback bitumen of the type described previously as filling mass for the oblong body 4. A mixture of this type, which is known in hydraulic engineering as S.R.O sand, is a cheap, easily deformable and coherent material which is highly suitable as a slopesealing filtering material and which as a rule is present at some distance below the waterline of the waterway 10 as the only slope revetment and is covered in most cases with a second revetment, for example formed of rubble, from above the waterline to some distance below the waterline.

The invention will now be illustrated by the following Example.

EXAMPLE Of a ship canal having slopes with a 1:4 gradient the slopes were provided over a length of 4 km with nets, each having a width of 10 m and a mesh of 25 cm, and made of rope consisting of polypropylene filament. The thickness of the rope was 5 mm. Fastened to the bot tom edge of each net, which extended 2.25 m below the water surface, were a number of roll-shaped bodies in end-to-end relationship. Each roll-shaped body had a length of m and a diameter of 30.5 cm. Each body consisted of a skin of polypropylene fabric with a weight of 1 10 g/m which enveloped a body mass consisting of 94.5 percent by weight of sand, 1.5 percent by weight of lime and 4 percent by weight of cutback bitumen (the cutback bitumen commercially available under the name Special Road Oil B.). At the upper end of the slope, where a horizontal section thereof on a level with the waterline adjoins the bank body of the waterway, the net was secured by means of stakes placed at intervals of 30 cm in the body of the dyke. The slope with the net laid thereon was subsequently lined with a mass similar to that used as filling mass for the roll-shaped bodies. This revetment was so applied as to extend 2.25 m below the water surface of the canal. The thickness of the revetment, starting at 45 cm below the water surface to the bottom edge of the revetment, was 30.5 cm. The thickness of the revetment from the water surface as far as 45 cm below the water surface was l5 cm. This thinner section was subsequently covered wlth a 20 cm thick layer of rubble,

which was rolled in the layer of S.R.O. sand by a roller.

I claim:

1. A support for a slope revetment comprising an oblong body which extends in the longitudinal direction of the slope and which is in supporting contact with the foot of the revetment and a carrier means from which the oblong body is suspended, said carrier means resting at least in part on the slope and being covered by the revetment.

2. The support of claim 1 in which the oblong body is substantially cylindrical with a diameter of from 0.8 to 1.5 times the thickness of the supported revetment.

3. The support of claim 1 in which the oblong body is formed by a skin which envelopes a deformable body mass.

4. The support of claim 1 in which the skin consists of a plastic.

5. The support of claim 4 in which the skin consists of a polypropylene fabric with a weight of from to grams per square meter.

6. The support-of claim 1 in which the deformable body mass contains sand and a cutback bitumen material.

7. The support of claim 6 in which the deformable body mass contains 90 to 96 percent by weight of sand, 1 to 37 percent by weight of lime and 1 to 9 percent by weight of cutback bitumen material.

8. The support of claim 1 in which the revetment has the same composition as the deformable body mass of the oblong body which supports the foot of the revetment.

9. The support of claim 1 in which the carrier means has the form of a net from which the oblong body is suspended.

10. The support of claim 9 in which the net is made from a rope consisting of polypropylene filaments.

11. The support of claim 9 in which the net is anchored by stakes driven into the slope.

12. A method for the protection of slope revetments against crumbling, which method comprises the stops of suspending an oblong body downwardly along the longitudinal direction of the slope from carrier means laid on the slope, covering the carrier means with a revetment, and extending the revetment downwardly along the longitudinal direction of the slope until contact is made with the oblong body, whereby the foot of the revetment is supported by the oblong body. 

1. A support for a slope revetment comprising an oblong body which extends in the longitudinal direction of the slope and which is in supporting contact with the foot of the revetment and a carrier means from which the oblong body is suspended, said carrier means resting at least in part on the slope and being covered by the revetment.
 2. The support of claim 1 in which the oblong body is substantially cylindrical with a diameter of from 0.8 to 1.5 times the thickness of the supported revetment.
 3. The support of claim 1 in which the oblong body is formed by a skin wHich envelopes a deformable body mass.
 4. The support of claim 1 in which the skin consists of a plastic.
 5. The support of claim 4 in which the skin consists of a polypropylene fabric with a weight of from 100 to 150 grams per square meter.
 6. The support of claim 1 in which the deformable body mass contains sand and a cutback bitumen material.
 7. The support of claim 6 in which the deformable body mass contains 90 to 96 percent by weight of sand, 1 to 37 percent by weight of lime and 1 to 9 percent by weight of cutback bitumen material.
 8. The support of claim 1 in which the revetment has the same composition as the deformable body mass of the oblong body which supports the foot of the revetment.
 9. The support of claim 1 in which the carrier means has the form of a net from which the oblong body is suspended.
 10. The support of claim 9 in which the net is made from a rope consisting of polypropylene filaments.
 11. The support of claim 9 in which the net is anchored by stakes driven into the slope.
 12. A method for the protection of slope revetments against crumbling, which method comprises the stops of suspending an oblong body downwardly along the longitudinal direction of the slope from carrier means laid on the slope, covering the carrier means with a revetment, and extending the revetment downwardly along the longitudinal direction of the slope until contact is made with the oblong body, whereby the foot of the revetment is supported by the oblong body. 